For the benefit of my fellow Boomkins, and anyone else interested, I'm posting about the most effective combat casting cycles for us in a DPS role.

Before I start, let me say that the bread and water stats of a raiding Balance Druid are spell damage, Intellect, and spell crit. With Lunar Guidance and Dreamstate, we get half or more of our mana regen from Intellect. It's also usually worthwhile to spec into Restoration enough to get Intensity for the bonus mana regen from Spirit, especially since endgame raid gear tends to have a lot of it.

Okay, now on to the spells, rated in terms of DPS and mana efficiency:

Wrath
* Highest DPS nuke when spammed (about 100 more than Starfire, at max rank).
* Poor mana efficiency compared to Starfire.
* Nature's Grace procs do not help this spell, due to the global cooldown.

Starfire
* Lower DPS than Wrath.
* Highest mana efficiency nuke. In fact, considering talents, this is the most efficient nuke in the game. It also scales better with spell damage than any other nuke in the game.
* Benefits significantly from Curse of Shadows.

Moonfire
* Very high DPS when spammed.
* Horrible mana efficiency when spammed.
* This is our worst spell in terms of efficiency, but due to the high talented crit rate, can make a good trigger for Nature's Grace as part of a casting cycle.

Insect Swarm
* Highest damage/mana in our arsenal.
* The debuff improves tanks' avoidance, so keep it up on mobs as much as possible.

Other spells of note:

Faerie Fire
* The armor debuff is not insignificant, but generally not worth it unless there's a melee DPS in the raid. A Feral Druid will usually provide and maintain the debuff if present.
* Improved Faerie Fire talent makes this very useful, as it improves melee DPS by approximately 3%, up to the +hit cap.

Innervate
* One of our most useful raid skills, this will refresh a significant portion of a mana-user's bar on a 6 minute timer.
* Effectiveness scales directly with Spirit, making it a generally poor choice for caster DPS, but excellent for healing Priests and Druids. Gear selection makes it less valuable for Shaman and Paladins.

Rebirth
* In-combat resurrection on a 30 minute timer, 2 second cast time.
* Restores 3200 health and mana to the target.
* Cannot be cast in Moonkin form.
* Costs 1600 mana.
* Using this spell costs the Balance druid a very large part of his mana pool, and requires that he stop doing DPS for the time it takes to shift out of Moonkin and cast it. Usually, it's not worth the extra 500 mana to shift back to Moonkin unless the death comes very early in the fight.
* Having to use Rebirth usually guarantees that the Balance Druid will go OOM during the later stages of a long fight.

Ok, now to the casting cycle.

Most mana-efficient
* Chain-cast Starfire, interrupting to refresh Insect Swarm when the debuff expires.
* Usually you'll get 4 SF casts to each IS.

Maximize crits
This is a slightly more interesting casting method that attempts to maximize Nature's Grace procs while minimizing the loss of potential DPS due to casting Wrath with Nature's Grace.
* In this method, you lead with Wrath or Starfire, followed by Insect Swarm.
* You will know if you got a NG proc by the time the global cooldown from IS is up, and therefore know whether to cast Wrath (no NG) or Starfire (NG) next.
* After Wrath or SF, cast Moonfire. Again, the delay for the GCD will let you know which to cast next.
* Continue the cycle with Starfire until your DoTs need refreshing. If you land a DoT and you don't have NG, cast Wrath; if you do have NG, cast Starfire.

As you can see, the fundamental idea is to use the break afforded by your DoTs to allow you to fire off Wrath in hopes of getting an NG proc by the time you resume Starfire casts, while hopefully never wasting NG on a Wrath cast and never losing time by cancelling a Wrath. Done properly, this technique will maximize your DPS while keeping a reasonable rate of mana consumption. The downside is that it requires good latency and nimble fingers on the casting keys.

Just ran some quick calculations for hit vs. crit for Moonkins, with a full raiding talent build. All figures include Moonkin Aura. Figures are based on spamming the spell nonstop with zero latency and don't take into account DoTs or other buffs/debuffs that may affect DPS. Misses are factored in, but resistances are not. Base spell miss is assumed to be 17%. Nature's Grace procs are included for Starfire (but don't affect Wrath because of the GCD).

I can extrapolate further if required, but the basic facts are pretty inarguable:
* 1% spell hit improves DPS by approximately 1%.
* 1% spell crit improves Wrath DPS by 1%, but Starfire DPS by around 1.2% - in fact, this ratio improves the more spell crit you stack. This is entirely due to the influence of Nature's Grace.